%F now shows the auth name or recepient name/address if the
message is from you.

Adds a message indicating the user's ability to :save or :pipe a message
with an unsupported mimetype and also adds a selector widget (similar to
the tutorial).

The selector widget was previously defined in the account wizard module,
so this commit breaks it out into its own module to allow for re-use.

Further, modify the BeginExLine() function to take an argument that
pre-populates the command line, allowing functions to initiate an ex
command without executing it.

Closes #95.

+ Changes NewComposer to return error.
+ Add lib to handle templates using "text/template".
+ Add -T option to following commands
    - compose.
    - reply
    - forward
+ Quoted replies using templates.
+ Forwards as body using templates
+ Default templates are installed similar to filters.
+ Templates Config in aerc.conf.
    - Required templates are parsed while loading config.
+ Add aerc-templates.7 manual for using template data.

creating a directory must not invoke the callback, as this is meant for the
completion of the move

Previously removing a tab would always pop from the history of tabs.
This checks to see if the closing tab is the one selected, if it is then
we use the history, otherwise we only need to change the selected tab if
it was after (to the right of) the closing tab, in which case we just
decrement the selected index.

A tab can now only be pushed onto the history if it is a selectable tab.

This reverts commit 1339faf7881f33762c6e0a4915404e362fc51de1.

This ensures that the search results follow the order of the current
sort so that cycling throught the results proceeds in displayed order.